Polymer blend for dispersion of particulate materials in aqueous systems

Abstract

Particulate materials in aqueous media such as heat exchange systems are dispersed by introducing into the system a polymer blend comprising about 50 to 99% by weight of (A) a water-soluble, dissociating, low molecular weight polymer of at least one alpha, beta-monoethylenically unsaturated carboxylic acid, and about 50 to 1% by weight of (B) a water-soluble, dissociating, lower molecular weight polymer selected from (1) vinyl aromatic polymers and (2) polymers of 2-acrylamido-2-methylpropanesulfonic acid. A typical polymer blend comprises, in neutralized form, (A) polyacrylic acid terminated with thioglycolic acid and (B) a polymer of sulfonated styrene and maleic anhydride.

I claim: 
     
       1. A method of dispersing particulate materials in an aqueous medium, which comprises introducing into the medium an amount effective to disperse said materials of a polymer blend consisting essentially of about 50 to 90% by weight of (A) a polyacrylic acid terminated by thioglycolic, bisulfite, or mercapto groups and about 50 to 1% by weight of (B) a water-soluble, dissociating low molecular weight polymer selected from the group consisting of (1) vinyl aromatic polymers and (2) polymers of 2-acrylamido-2-methylpropane sulfonic acid. 
     
     
       2. The method of claim 1 wherein the vinyl aromatic polymers (1) are selected from the group consisting of hydrolyzable styrene/maleic anhydride copolymer, hydrolyzable sulfonated styrene/maleic anhydride copolymer, hydrolyzable styrene/maleimide copolymer, hydrolyzable sulfonated styrene/maleimide copolymer, sulfonated polystyrene, and copolymers of sulfonated styrene and divinyl benezene, and polymers (2) are selected from the group consisting of homopolymers of 2-acrylamido-2-methylpropane sulfonic acid and copolymers of 2 acrylamido-2-methylpropane sulfonic acid and at least one water soluble comonomer. 
     
     
       3. The method of claim 1 wherein the amount of polymer (A) is about 70 to 95% by weight and the amount of polymer (B) is about 30 to 5% by weight. 
     
     
       4. The method of claim 1 wherein polymer (B) is a hydrolyzable polymer of sulfonated styrene and maleic anhydride. 
     
     
       5. The method of claim 4 wherein the amount of polymer (A) is about 70 to 95% by weight and the amount of polymer (B) is about 30 to 5% by weight. 
     
     
       6. The method of claim 1 wherein the number average molecular weight of polymers (A) and (B) is about 500 to 5000.